It has been reported that the amino acid sequence of Ecto-nucleotide pyrophosphatase/phosphodiesterase 4 (ENPP4) derived from human and the DNA coding the sequence, and however its function has not been demonstrated (Patent Document 1, Patent Document 2, Patent Document 3, Patent Document 4, Patent Document 5, Patent Document 6). It has been reported that the amino acid sequence of Ecto-nucleotide pyrophosphatase/phosphodiesterase 5 (ENPP5) derived from human and the DNA coding the sequence, and however its function has not been demonstrated (Patent Document 7, Patent Document 8, Patent Document 9, and Non-Patent Document 1). It has been reported that the amino acid sequence of Ecto-nucleotide pyrophosphatase/phosphodiesterase 6 (ENPP6) derived from human and the DNA coding the sequence (Patent document 10, Patent document 11, Non-Patent Document 1, Non-Patent Document 2). It has been reported that ENPP6 has phosphodiesterase/phosphomonoesterase (PDE/PME) activity and phospholipase C (PLC) activity and also Choline-specific Glycerophosphodiester Phosphodiesterase activity and degrades LPC, SPC, and GPC (Non-Patent Document 3).    Patent Document 1: International Publication No. WO 99/18126    Patent Document 2: International Publication No. WO01/77137    Patent Document 3: International Publication No. WO02/08278    Patent Document 4: International Publication No. WO01/34768    Patent Document 5: US Patent No. 2003/104426    Patent Document 6: US Patent No. 2002/193567    Patent Document 7: US Patent No. 2003/022331    Patent Document 8: International Publication No. WO01/55358    Patent Document 9: International Publication No. WO01/60860    Patent document 10: US Patent No. 2003/215909    Patent document 11: EP Patent No. 1293569    Non-Patent Document 1: Genome Res., 13, 2265-2270, 2003    Non-Patent Document 2: Nat. Genet., 36, 40-45, 2004    Non-Patent Document 3: J. Biol. Chem., 280, 23084-93, 2005